We can tell our universe is expanding because if the ‘red shift’ of light from distant galaxies.
You can think of light as a wave, with peaks and dips. The distance between 2 peaks is called the wavelength. Different colours of light have different wavelengths – blue light has a shorter wavelength than red light.
When light is moving towards you the peaks get squashed up so it gets bluer. When it’s moving away from you the peaks get stretched out so it looks redder.
This is how we know that the universe is expanding, because far away galaxies emit redder light. It’s very useful for working out how fast things are going!
I’m with Jack on this one. Light of objects moving away is stretched – think of a tennis ball on a spring and what happens to the spring coils if you throw it away from you – they get pulled apart.
The longest wavelength of the light we can actually see is at the red end of the rainbow (red, orange, yellow green blue, indigo, violet) so, to make this theory more understandable we often call it the “red shift”. the actual effect is called the “Doppler effect”.
You will have surely experienced this when an ambulance or police car has passed you at speed with its siren on. The “de dah de dah” noise it makes takes on a different tone as it goes past. This is because, as it approaches, the sound waves (which are equivalent to light waves for this discussion) are being squashed and as it goes away they are stretched. The last bit is the “red shift”
OK – I’m getting there now. We can detect that light from stars is more stretched (in other words at a longer wavelength) the further away they are so they must be moving away from us. So the universe is getting bigger – currently.
I don’t think anyone really knows what is going to happen next.
I’m no astrologist!!! Truely not my area – but I would think that if there were huge changes out there they would affect planet Earth more seriously and put our laws of physics out of balance. Have you been watching “Orbit” on TV – fascinating stuff!!! 🙂